Southwest Florida Shelf Research Articles

Dynamic Satellite Seascapes as a Biogeographic Framework for Understanding Phytoplankton Assemblages in the Florida Keys National Marine Sanctuary, United States

Physical, chemical, geological, and biological factors interact in marine environments to shape complex but recurrent patterns of organization of life on multiple spatial and temporal scales. These factors define biogeographic regions in surface waters that we refer to as seascapes. We characterize seascapes for the Florida Keys National Marine Sanctuary (FKNMS) and southwest Florida shelf nearshore environment using multivariate satellite and in situ measurements of Essential Ocean Variables (EOVs) and Essential Biodiversity Variables (EBVs). The study focuses on three periods that cover separate oceanographic expeditions (March 11-18, May 9-13, and September 12-19, 2016). We collected observations on bio-optical parameters (particulate and dissolved spectral absorption coefficients), phytoplankton community composition, and hydrography from a ship. Phytoplankton community composition was evaluated using 1) chemotaxonomic analysis (CHEMTAX) based on high-performance liquid chromatography (HPLC) pigment measurements, and 2) analysis of spectral phytoplankton absorption coefficients (aphy). Dynamic seascapes were derived by combining satellite time series of sea surface temperature, chlorophyll-a concentration, and normalized fluorescent line height (nFLH) using a supervised thematic classification. The seascapes identified areas of different salinity and nutrient concentrations where different phytoplankton communities were present as determined by hierarchical cluster analyses of HPLC pigments and aphy spectra. Oligotrophic, Mesotrophic and Transition seascape classes of deeper offshore waters were dominated by small phytoplankton ( 60 %). Spectral analysis of aphy indicated higher absorption levels at 492 and 550 nm wavelengths in seascapes carrying predominantly small phytoplankton than in classes dominated by larger taxa. Seascapes carrying large phytoplankton showed absorption peaks at the 673 nm wavelength. The seascape framework promises to be a tool to detect different biogeographic domains quickly, providing information about the changing environmental conditions experienced by coral reef organisms including coral, sponges, fish and higher trophic levels. The effort illustrates best practices developed under the Marine Biodiversity Observation Network (MBON) demonstration project, in collaboration with the South Florida Ecosystem Restoration Research (SFER) project managed by the Atlantic Oceanographic and Meteorological Laboratory of NOAA (AOML-NOAA).

An analytic solution for bottom intensified flow along sloping topography

A self-similar nonlinear analytic solution is derived for a case of isolated deep flow over broad sloping topography. The solution takes the form of an arctangent function and physically manifests as a compressing jet (narrowing and intensifying) with Ekman pumping controlling the interface evolution. Notably, this jet travels in the direction with shallow water to the left, which is in contrast to the expected flow direction of topographic Rossby wave propagation (shallow water to the right). Such deep flows are not accessible via satellite observations and play an important role ocean-coastal ocean connectivity. Examples of deep flows over broad shelves include the South Atlantic Bight and West Florida Shelf, where deep upwelling is thought to influence the generation of red tides, local ecosystems, and deep carbon sequestration. Relevance of the analytic solution to the South Atlantic Bight circulation is provided.

Determining the Sources of Macroalgae During Beach Stranding Events from Species Composition, Stable Isotope Analysis, and Laboratory Experiments

Large accumulations of stranded macroalgae on the beaches of Sanibel Island from 2004 to 2007 were unusual and thought to be driven by high rainfall and river flows stemming from a high frequency of hurricanes. The southwest Florida shelf was thought to be isolated from far-field effects such as high river flows and urbanization but field- and laboratory-based studies suggest that nitrogen enrichment, fragmentation, and species composition of macroalgal communities on the shelf and in the estuary contribute to beach stranding events. Macroalgae were sampled using a belt transect method to determine species distribution and abundance. Macroalgae were abundant (1) in the lower estuary with abundant seagrass and (2) on limestone outcroppings in the Gulf of Mexico. An MDS analysis of the quadrat samples indicated two distinct macroalgal community types, a “Sound” assemblage around Pine Island Sound and a “Gulf” assemblage, associated with a live bottom and patch reef in the Gulf of Mexico. Peak abundances for the two community types differed with the Gulf having peak abundances from July to November, while peak abundances in the Sound occurred from January to July. Sound macroalgal tissue had significantly enriched δ15N compared to Gulf tissue when all species were combined and in five of six species collected at both locations suggesting that stable isotope analysis could be useful in combination with species composition in determining the source of macroalgae during stranding events. In addition, a laboratory study was conducted on four species that were sampled and frequently collected as a result of stranding events. Laboratory growth experiments demonstrated the potential for three of four common species (Solieria filiformis, Gracilaria tikvahiae, Agardhiella subulata) to fragment and grow significantly more under elevated nitrate conditions.

Modeling the impacts of the Loop Current on circulation and water properties over the Pulley Ridge region on the Southwest Florida shelf

A high-resolution (∼1.5km) regional ocean model was developed for the southern Florida Shelf and Florida Straits. A two-year (2011–12) simulation was conducted and the model results were generally in good agreement with available satellite and in situ data. Model results show that the meandering of the Gulf of Mexico Loop Current (LC) exerts strong impacts on the dynamics over Pulley Ridge on the southwest Florida shelf, where the LC turns into the Florida Straits to become the Florida Current (FC). In particular, the northward migration of the LC/FC front often drives strong on-shelf (eastward) transport of the slope water onto the shelf of southern Pulley Ridge, an important mesophotic coral reef at depths between 60 and 90m. Frequent remotely or locally generated eddies over the western slope of Pulley Ridge may be blocked by the northern LC/FC front when it is closely in contact with the shelf break, a phenomenon documented in previous studies. These eddies drive strong upwelling of slope water toward the shelf break, which sometimes can extend 20–30km onto the shelf, strongly affecting the Pulley Ridge region. A narrow return flow, largely along the shelf edge from Florida Keys to Pulley Ridge, may be produced when the FC impinges upon the continental slope during late fall to early spring. The results from an experiment without the surface winds suggest that wind forcing contributes to the westward flow but is not the determining factor for its generation.

Mississippi waters reaching South Florida reefs under no flood conditions: synthesis of observing and modeling system findings

In August 2014, in situ measurements revealed an intense salinity drop impacting South Florida coral reefs, between Pulley Ridge (Southwest Florida Shelf) and the Florida Keys. The low salinity waters had a surface signal of 32 (down from 35.2) and extended over a 15–20-m deep lens. Satellite observations showed that this abrupt drop in salinity was due to a southeastward export of Mississippi River waters from the Northern Gulf of Mexico (GoM), revealing strong interaction between coastal and oceanic flows. Unlike previous events of marked long-distance Mississippi water export, this episode is not associated with Mississippi flooding conditions, which makes it a unique study case. We have developed a high-resolution (~2 km) comprehensive hydrodynamic numerical model of the GoM to study the conditions that controlled the 2014 Mississippi River water export episode. It is based on the Hybrid Coordinate Ocean Model (HYCOM) and assimilates remotely sensed altimetry and sea surface temperature observations, to ensure that the simulated upper-ocean is realistic. This regional model has a detailed representation of coastal physics (especially river plume dynamics) and employs high-frequency river discharge and atmospheric forcing. The combined use of the simulation and observations reveals a unique pathway that brought Mississippi waters first eastward along the Northern GoM continental shelf, under prevailing winds and the presence of an anticyclonic Loop Current eddy, then southward along the edge of the West Florida Shelf, before reaching the deep GoM. Unlike usually observed, the offshore advection of Mississippi River waters thus took place far from the Delta area, which is another specificity of the 2014 episode. Finally, in the Florida Straits, Mississippi waters were advected from the deep ocean to the continental shelf under the influence of both deep sea (particularly a cyclonic Loop Current frontal eddy) and shelf flows (wind-induced Ekman transport). The simulation, in tandem with data, thus helped analyze processes that are likely to affect the connectivity between reefs in the southern Florida region (Florida Keys, Dry Tortugas, Pulley Ridge) and remote areas (Mississippi Delta), as well as the local connectivity between neighboring reefs.

Toward connecting subtropical algal blooms to freshwater nutrient sources using a long-term, spatially distributed, in situ chlorophyll-a record

Harmful algal blooms are increasing in tropical estuaries which can have complex morphologies and hydrologic regimes while being less well studied than temperate estuaries. Spatial and temporal patterns of algal bloom occurrence in Florida Bay were examined to evaluate the potential contribution of the various freshwater inputs to the subtropical bay as nutrient sources. Monthly water quality data, from 1989 to 2009, at 28 sampling stations across the bay were analyzed at the station-month level, aggregated into hydrologic Zones of Similar Influence and based on annual rainfall seasons. The Zones of Similar Influence are linked to the geomorphology of the bay with western areas being more directly connected to the Southwest Florida Shelf waters than eastern areas. Correlation analysis suggested that inputs of phosphorus were the predominant factor in the initiation of elevated chlorophyll a (chl-a) levels but was also consistent with higher nitrogen limitation in western Florida Bay as reported in literature. Differences in mean monthly chl-a indicated a seasonality of algal blooms with elevated chl-a concentrations following heavy precipitation months for stations in the north-central and western areas of the bay where algal blooms have been re-occurring. Differences in stations' chl-a concentrations showed stations to the northwest as having significantly higher concentrations than more interior stations during the dry season but not during the rainy season (when algal blooms are occurring). Mapping the sampling stations atop the bathymetry of Florida Bay highlighted the importance of coastal morphology in evaluation of potential nutrient pathways for estuarine algal bloom sources. The specific factors resulting in the seasonal cycles of blooms remained unresolved but portions of the bay and times of year were identified as important areas for further research. This study indicates that illustrating the interplay of geomorphology and winds and rains at fine temporal and spatial resolution is required to describe nutrient circulation for systems with complex morphologies such as those associated with reefs, island matrices and headlands.

New data on lithistid sponges from the deep Florida shelf with description of a new species ofTheonella

Most lithistids occur worldwide in deep-water environments, but can be found in some places in shallow water. They are not well known in the tropical western Atlantic, despite the fact that they were first described in the late 1800s. We report here two species of poorly known theonellid demosponges (Astrophorina),Discodermia dissolutaandTheonella atlantica, and one new species,Theonella wrightae, from the north-west, south-west and south Florida shelf. There is considerable variability in habitus, colour and spiculation in this species. If samples are taken randomly from different specimens and from functionally and structurally different locations on the sponge, the specimens could be mistakenly identified or individuals of the same species could be described as different species. This report increases the number of lithistid sponges reported from the tropical western Atlantic region to 30 species, but our unpublished data suggest a much higher number of species present in this region. It is also the second report of the relatively deep-water (81 m) occurrence ofD. dissolutathat is mostly known from depths as shallow as 10–30 m.

Modeling Larval Transport and Settlement of Pink Shrimp in South Florida: Dynamics of Behavior and Tides

AbstractThe pink shrimp Farfantepenaeus duorarum, one of the commercially important Penaeidae, reproduces offshore of the southwest Florida (SWF) shelf. Larvae migrate to nursery grounds in estuarine Florida Bay. Using a numerical approach, we investigated the role of spawning location, larval traits, and physical forces on the transport of pink shrimp larvae. First, the Regional Oceanic Modeling System that is based on tides, air–ocean fluxes, and freshwater flows was used to simulate the SWF shelf oceanography. The model replicates the tides, winds, salinity, currents, and seasonality of the shelf. Secondly, the Regional Oceanic Modeling System was coupled offline with the Connectivity Modeling System, in which virtual larvae were released near the surface from two spawning sites, Dry Tortugas and Marquesas, and tracked until the time for settlement (about 28–30 d). Virtual larvae moved vertically in the water column following ontogenetic behaviors previously observed in the field: diel vertical migration (DVM) and selective tidal stream transport (STST). Lagrangian trajectories indicated that migration paths changed radically between summer and winter during model years (1995–1997). Maximum settlements occurred in summer by larvae crossing the SWF shelf, while the lowest settlement occurred in winter by larvae moving through passes in the Florida Keys. Modeling results demonstrated an effective east‐northeast transport across the SWF shelf during summer as a result of the tidal currents, the subtidal currents, and the combined DVM and STST behaviors. The current phase captured during the initial DVM period was critical to determine the direction in which larvae move, favorable (east and northward) or unfavorable (south and westward), before the STST behavior captures the eastward tidal current that brings larvae to the nursery grounds. Unfavorable currents were driven by the summer easterlies and low salinities at the coast. Results indicated that Marquesas is the more effective spawning ground, with 4.5 times more likely settlement of originating larvae compared with Dry Tortugas. Model‐estimated seasonal settlement patterns concurred with postlarval influxes previously observed at Florida Bay boundaries.Received June 26, 2014; accepted December 7, 2014

Effect of submarine groundwater discharge on the coastal ocean inorganic carbon cycle

Using radium (Ra) isotopes, we estimate that the average submarine groundwater discharge (SGD) flux (marine plus terrestrial groundwater) into the southwest Florida Shelf (SWFS) was 20 ± 10 × 107 and 18 ± 8 × 107 m3 d−1 in July and October 2009, respectively. The terrestrial groundwater flux was the same order of magnitude as the local river discharge in July 2009. Shelf‐water total alkalinity (TAlk) and dissolved inorganic carbon (DIC) concentrations could not be explained by river inputs alone, suggesting a groundwater source. We estimated SGD fluxes of TAlk and DIC using the SGD flux derived from a shelf‐water 226Ra budget and TAlk and DIC concentration differences between the groundwater and seawater. These fluxes were also determined by the observed TAlk : 226Ra and DIC : 226Ra relationships in the shelf water, and the 226Ra flux sustained by SGD. These TAlk and DIC fluxes were 11–71 times more than the combined input of local rivers, suggesting that SGD was the dominant source of TAlk and DIC to the SWFS during 2009. SGD is an important component of the inorganic carbon budget for the coastal ocean.

Microbial production along the West Florida Shelf: Responses of bacteria and viruses to the presence and phase of Karenia brevis blooms

Bacterial abundance, production, protein and nucleic acid synthesis, growth, and viral abundance were measured in waters associated with three bloom stages of the “red tide” dinoflagellate Karenia brevis along the south West Florida Shelf (WFS). Measurements were taken: (1) when no bloom was present; (2) during the initiation stage of a bloom; and (3) during the maintenance stage of a bloom. Results indicate that the bacterial community was nutrient limited in the non-bloom period, with highest abundance and production rates occurring near and within estuaries. Abundance of virus like particles (VLPs) was higher within estuaries, but we hypothesize VLPs were not a high source of bacterial mortality, possibly due to high decay rates due to UV degradation or extracellular nucleases. High bacterial production, balanced protein to nucleic acid synthesis, and statistically similar bacteria abundances measured on consecutive days within the initiating bloom suggest a highly productive community with equally high mortality. VLP abundance declined during the first 48h within both bloom stages, suggesting that viral genomes were either within host cells (not evident in water column samples), or bacterial mortality was due to mixotrophic grazing by K. brevis. Using a conservative grazing rate of 1bacteriaK. brevis−1h−1, K. brevis grazing could account for >100% of bacterial mortality during an initiating bloom. Bacterial abundance and production were significantly decreased and protein to nucleic acid synthesis became unbalanced during the maintenance phase bloom. An increase in VLP abundance during the maintenance phase was most likely the cause of bacterial mortality as mixotrophic grazing could only account for ∼4% of the change in bacterial abundance. Together, these data suggest that the associated bacteria and viruses play a critical role in the formation and termination of K. brevis blooms.

Ecological condition and value of oyster reefs of the Southwest Florida shelf ecosystem

The eastern oyster Crassostrea virginica is prolific and their reefs are dominant features along the estuaries and coastal areas in the Gulf of Mexico including those along the Southwest Florida coast. This paper examines the ecological and indirect economic value of oysters and the ecosystem services they provide. Drivers of change in reefs as well as various factors (pressures) that affect oyster reefs are examined. Using the monitoring data from on-going studies, this study examined various metrics of oyster health, reproduction and survival to develop an index to create an overall state of oyster reefs in the Southwest Florida estuaries. Based on existing data, oyster reefs in Southwest Florida estuaries are at “caution”, but stable. Restoration of a more natural freshwater inflow, minimizing nutrient and contaminant input as well as decreased sedimentation will enable oyster reefs to expand and thrive.

On the temporal variation of DOM fluorescence on the southwest Florida continental shelf

Dissolved organic matter (DOM) plays a crucial role in the nutrient and carbon cycling in the coastal-shelf-ocean boundary. It is a major reservoir of reduced carbon and carries important information on how sea and landscape have been modified. Due to the complexity of the biogeochemical processes in this boundary, its distribution is not well understood. This study evaluated the Excitation Emission Matrix (EEM) fluorescence method combined with Parallel Factorial Analysis (PARAFAC) modeling to resolve DOM fluorescence components, and their distribution from near-shore to off-shore on the southwest (SW) Florida Shelf. The PARAFAC model derived identified five unique DOM components from 272 Excitation and Emission Matrix (EEM) samples measured across the shelf on May and October 2008, and January and April 2009 cruises. These five different fluorophores consisted of two humic-like components that were attributed to natural (component1: HLC1) and anthropogenic (component 2: HLC2) sources; an unidentified component (component 3); two autochthonous protein components, identified as tryptophan-like (component 4:TLC4); and tyrosine-like (component 5:TLC5) fluorophores. The observed temporal variations of terrestrial and anthropogenic humic-like DOM fluorescent materials were not necessarily dependent on the timing of river runoffs and rainfall frequency on the shelf, but also on other factors (i.e., suspension of sediments in shallow water induced by wind-driven mixing, dilution, hypersalinity conditions). The areal distribution of the resolved terrestrial DOM fluorescence on the mid-shelf indicates evidence of offshore transport of land-derived materials. The evident terrestrial humic-like inputs into the shelf correspond to the increase in the protein-like fluorescence, which was attributed to autochthonous biological degradation. Results from this study demonstrated advances in several aspects of monitoring the temporal distribution of DOM on the continental shelf of Florida using EEM and PARAFAC methods. The methods employed were able to: (1) resolve sources of the individual DOM fluorescence components of the bulk DOM; (2) generate spatial and temporal distribution maps of each of the components on the shelf; and (3) provide insights into biological, chemical, and physical processes that control the DOM variability of each of the resolved DOM components.

Resolving DOM fluorescence fractions during a Karenia brevis bloom patch on the Southwest Florida Shelf

Organic matter can be supplied naturally from land through rivers or produced in-situ in the marine environment. Current methods of examining natural bulk dissolved organic matter (DOM) are not able to discriminate multiple sources of DOM. A diagnostic tool to identify DOM sources is critical to determine possible sources of organic nutrients that influence K. brevis harmful algal bloom (HAB) development. This study applied multi-wavelength fluorescence coupled with a supervised pattern recognition technique (e.g., parallel factorial analysis (PARAFAC) using samples collected from river, estuary and shelf waters where the toxic dinoflagellate Karenia brevis off of Sanibel Island, Florida was observed. The PARAFAC model distinguished four different fractions of DOM components containing humic-like and protein-like components. The derived terrestrial humic-like material was indicative of land-based sources while the tryptophan-like component was likely produced from in-situ biological production. The study developed and tested the hypothesis that the direct relationship of the protein-like DOM fluorescence with K. brevis cell density indicated that the bloom patch was most likely supported by organic nutrients produced in-situ. The results demonstrated that multi-wavelength fluorescence analysis coupled with PARAFAC modeling technique simultaneously resolved DOM fluorescence fractions and their possible sources—information that are critical in explaining harmful algal bloom formation.

Detection of Karenia brevis blooms on the west Florida shelf using in situ backscattering and fluorescence data

Using shipboard data collected from the central west Florida shelf (WFS) between 2000 and 2001, an optical classification algorithm was developed to differentiate toxic Karenia brevis blooms (>10 4 cells l −1) from other waters (including non-blooms and blooms of other phytoplankton species). The identification of K. brevis blooms is based on two criteria: (1) chlorophyll a concentration ≥1.5 mg m −3 and (2) chlorophyll-specific particulate backscattering at 550 nm ≤ 0.0045 m 2 mg −1. The classification criteria yielded an overall accuracy of 99% in identifying both K. brevis blooms and other waters from 194 cruise stations. The algorithm was validated using an independent dataset collected from both the central and south WFS between 2005 and 2006. After excluding data from estuarine and post-hurricane turbid waters, an overall accuracy of 94% was achieved with 86% of all K. brevis bloom data points identified successfully. Satisfactory algorithm performance (88% overall accuracy) was also achieved when using underway chlorophyll fluorescence and backscattering data collected during a repeated alongshore transect between Tampa Bay and Florida Bay in 2005 and 2006. These results suggest that it may be possible to use presently available, commercial optical backscattering instrumentation on autonomous platforms (e.g. moorings, gliders, and AUVs) for rapid and timely detection and monitoring of K. brevis blooms on the WFS.

Evaluation of Global Ocean Data Assimilation Experiment products on South Florida nested simulations with the Hybrid Coordinate Ocean Model

The South Florida Hybrid Coordinate Ocean Model (SoFLA-HYCOM) encompasses a variety of coastal regions (the broad Southwest Florida shelf, the narrow Atlantic Keys shelf, the shallow Florida Bay, and Biscayne Bay) and deep regions (the Straits of Florida), including Marine Protected Areas (the Florida Keys Marine Sanctuary and the Dry Tortugas Ecological Reserve). The presence of the strong Loop Current/Florida Current system and associated eddies connects the local and basin-wide dynamics. A multi-nested approach has been developed to ensure resolution of coastal-scale processes and proper interaction with the large scale flows. The simulations are free running and effects of data assimilation are introduced through boundary conditions derived from Global Ocean Data Assimilation Experiment products. The study evaluates the effects of boundary conditions on the successful hindcasting of circulation patterns by a nested model, applied on a dynamically and topographically complex shelf area. Independent (not assimilated) observations are employed for a quantitative validation of the numerical results. The discussion of the prevailing dynamics that are revealed in both modeled and observed patterns suggests the importance of topography resolution and local forcing on the inner shelf to middle shelf areas, while large scale processes are found to dominate the outer shelf flows. The results indicate that the successful hindcasting of circulation patterns in a coastal area that is characterized by complex topography and proximity to a large scale current system requires a dynamical downscaling approach, with simulations that are nested in a hierarchy of data assimilative outer models.

Sensitivity of bacterioplankton nitrogen metabolism to eutrophication in sub-tropical coastal waters of Key West, Florida

Expression of intracellular ammonium assimilation enzymes were used to assess the response of nitrogen (N) metabolism in bacterioplankton to N-loading of sub-tropical coastal waters of Key West, Florida. Specific activities of glutamine synthetase (GS) and total glutamate dehydrogenase (GDH T) were measured on the bacterial size fraction (<0.8 μm) to assess N-deplete versus N-replete metabolic states, respectively. Enzyme results were compared to concentrations of dissolved organic matter and nutrients and to the biomass and production of phytoplankton and bacteria. Concentrations of dissolved inorganic N (DIN), dissolved organic N (DON), and dissolved organic carbon (DOC) positively correlated with specific activities of GDH T and negatively correlated with that of GS. Total dissolved N (TDN) concentration explained 81% of variance in bacterioplankton GDH T:GS activity ratio. The GDH T:GS ratio, TDN, DOC, and bacterial parameters decreased in magnitude along a tidally dynamic trophic gradient from north of Key West to south at the reef tract, which is consistent with the combined effects of localized coastal eutrophication and tidal exchange of seawater from the Southwest Florida Shelf and Florida Strait. The N-replete bacterioplankton north of Key West can regenerate ammonium which sustains primary production transported south to the reef. The range in GDH T:GS ratios was 5–30 times greater than that for commonly used indicators of planktonic eutrophication, which emphasizes the sensitivity of bacterioplankton N-metabolism to changes in N-bioavailability caused by nutrient pollution in sub-tropical coastal waters and utility of GDH T:GS ratio as an bioindicator of N-replete conditions.

Nutrient quality drives differential phytoplankton community composition on the southwest Florida shelf

During May 2003, the dry season, the southwest Florida shelf was surveyed for nutrient concentrations and phytoplankton community composition concurrently with plankton nutritional and physiological status (tracer techniques, enzyme assay, and biomass response bioassays). Inorganic nitrogen concentrations were low throughout the region, while dissolved organic nitrogen (DON) was elevated (&gt;30 µmol N L−1) nearshore. Conversely, PO43‐ and dissolved organic phosphorus concentrations were high only in northern coastal areas adjacent to estuarine outflows. Nitrogen : phosphorus (N : P) ratios in the particulate material; gradients in NO3− and urea uptake rates; urease and alkaline phosphatase activities; and bioassay responses were indicative of a strong gradient from N to P limitation of plankton biomass from north to south. Nitrogen limitation was apparent in the northern region (N : Pparticulate &lt; 8, Tampa to Sanibel), where PO43‐ and DON inputs dominated; balanced nutrient conditions were evident in the mid‐region (N : Pparticulate = 8−24, Sanibel to Shark River); and P limitation was evident south of the Shark River (N : Pparticulate &gt; 24), where inorganic N input was greatest. Phytoplankton community composition varied along the same gradient, from a cyanobacteria and dinoflagellate community in the north, to a cyanobacteria‐dominated community in the mid‐region, and to a diatom community in the southern region. Percentages of NO3− uptake and diatoms in the total phytoplankton community were positively related, as were percentages of urea uptake and cyanobacteria. Inorganic and organic N and P fractions in the nearshore shelf region reflect longitudinal gradients in regional watershed characteristics, and their relative availability thus appeared to control both phytoplankton community composition and its physiological status.

CDOM distribution and CO 2 production on the Southwest Florida Shelf

Partial pressures of carbon dioxide ( pCO 2) were measured in river and coastal waters on two cruises in November 1999 and June 2000 on the Southwest Florida Shelf. Supersaturation with respect to the atmosphere was observed for most river and near-shore waters in November 1999. pCO 2 ranged from 403 μatm in the Gulf of Mexico to 1280 μatm in the Shark River. The coastal waters of the Southwest Florida Shelf had unusually low salinities at this time due to high inputs of freshwater runoffs after Hurricane Irene. In general, pCO 2 levels decreased with increasing salinity, but at different gradients for the different river systems. In June 2000, salinity gradients were considerably reduced during this drought year, with hypersalinity indicating reduced freshwater inputs. However, high pCO 2 levels were still observed in and near the mouth of the Shark River ( pCO 2=383–1280 μatm). A positive correlation of pCO 2 levels with colored dissolved organic matter (CDOM) and chlorophyll was observed in all systems examined. CO 2 in natural waters may be produced from the photochemical degradation of CDOM, microbial respiration or via shifts in the carbonate equilibrium. Some evidence for a small contribution from photochemical production was observed in the Shark River mouth in a dry season diel study, but not in the wet season. Differences between the rivers are primarily attributed to the significantly higher total alkalinity and lower pH values in the Shark River, and associated higher pCO 2 levels. In general, spatial variability in pCO 2 is dominated by the chemical characteristics of the river inputs, with temporal variability modulated by changes in pH, photochemical production in low flow seasons and draw down by primary production.

NORMJONESIA DANIELI, A NEW GENUS AND SPECIES OF NANNASTACID CUMACEAN (MALACOSTRACA: PERACARIDA) FROM THE SOUTHWEST FLORIDA CONTINENTAL SHELF

Abstract The nannastacid cumacean, Normjonesia danieli, n. g., n. sp., is described from a depth of 88 m on the Southwest Florida shelf in the southeastern Gulf of Mexico. The new genus appears to have its closest affinities with Campylaspis Sars and Cubanocuma Bacescu and Muradian, also known from the shallow waters of the Caribbean Sea. A combination of characters, including: (1) the apparent lack of terminal aesthetes on antenna 1; (2) the absence of exopods on the female; (3) the presence of 5 pairs of exopods on the male; and (4) the presence of long terminal setae on the third maxilliped, distinguishes Normjonesia from the other known genera of the family Nannastacidae.

Normjonesia Danieli, a New Genus and Species of Nannastacid Cumacean (Malacostraca: Peracarida) from the Southwest Florida Continental Shelf

The nannastacid cumacean, Normjonesia danieli, n. g., n. sp., is described from a depth of 88 m on the Southwest Florida shelf in the southeastern Gulf of Mexico. The new genus appears to have its closest affinities with Campylaspis Sars and Cubanocuma Băcescu and Muradian, also known from the shallow waters of the Caribbean Sea. A combination of characters, including: (1) the apparent lack of terminal aesthetes on antenna 1; (2) the absence of exopods on the female; (3) the presence of 5 pairs of exopods on the male; and (4) the presence of long terminal setae on the third maxilliped, distinguishes Normjonesia from the other known genera of the family Nannastacidae.